As traffic over Internet Protocol (IP) networks and other type of networks continues its rapid growth, and with the growth of the variety of multimedia conferencing equipment, more and more people use multimedia conferencing as their communication tool. A plurality of videoconferencing types of session require content to be presented with the video image. Business meetings, educational sessions, lectures, marketing presentations, professional meetings (such as design reviews), etc. require content presentation. Different types of content such as EXCEL® tables, POWERPOINT® presentations, slides, charts, drawings, etc. may be presented during a video conferencing session. EXCEL and POWERPOINT are registered trademarks of Microsoft Corporation.
Usually the content is important for understanding the current discussion; therefore, the content is delivered to all the conferees. Today, at a delivery endpoint, content is converted to video stream by capturing, few times per second, the image of the screen of the computer that runs the presentation. Then the video stream of the presentation may be compressed by an encoder in addition to the encoder that is used for handling the video stream of the conference. In most cases, the frame rate used by the encoder to compress the content is low, 1 to 10 frames per second for example. The compressed content may be sent from the delivery endpoint toward a multipoint control unit (MCU) over a separate stream using a different channel than the endpoint video image. From the MCU the content may be sent toward one or more receiving endpoints as video switching over a separate stream other than the continuous presence video image of the conference. The parameters of the content encoder are negotiated to the highest common parameters. In some video conferences, the MCU may transcode the content that is sent toward one or more receiving endpoints. Further, for some limited endpoints that cannot handle the content as a separate video stream, the MCU may treat the content as a video stream from an endpoint, and may add it to a segment in the continuous presence video image that is targeted toward the limited receiving endpoints.
An MCU is a conference controlling entity that is typically located in a node of a network or in a terminal that receives several channels from endpoints. According to certain criteria, the MCU processes audio and visual signals and distributes them to a set of connected channels. Examples of MCUs include the MGC-100™, RMX 2000®, which are available from Polycom, Inc. (MGC-100 is a trademark of Polycom, Inc. RMX-2000 is a registered trademark of Polycom, Inc.) A terminal, which may be referred to as an endpoint, is an entity on the network, capable of providing real-time, two-way audio and/or video and/or content visual communication with another endpoint or with an MCU. A more thorough definition of an endpoint and an MCU may be found in the International Telecommunication Union (“ITU”) standards, such as but not limited to the H.120, H.324, and H.323 standards, which may be found at the ITU website: www.itu.int.